1. Field of the Invention
This invention relates in general to archery arrows and, more particularly, to arrow nocks affixed to the arrows which receive the bowstring.
2. Prior Art
Conventional arrow nocks are ordinarily made of lightweight metal or plastic and are subject to breakage due to the substantial stresses which are imparted by the bowstring to the nock which in turn transmits such stresses to the arrow during shooting. It has been found that these stresses result in substantial flexing of the connection between the nock and the arrow. This flexing of the nock connection and inconsistent flexing of the nock itself substantially detract from shooting accuracy. The problem is compounded by either intended or unintended off center loading of arrow nocks by highly skilled target archers and the fact that the nock material is usually constructed of plastic which is substantially weaker than the material of which the arrow is constructed. Accordingly, the nock rather than the arrow is subject to fatigue failure and repeated shooting results in increased flexing of the connection until failure occurs at which time the nock is simply replaced.
High level target archery requires precise fine tuning of the arrows to the bow to obtain consistent results. The objective here is to substantially achieve one complete cycle of arrow flexing as the arrow leaves the bow so that the two bending nodes of the arrow remain aligned with the target and so that the fletch does not contact the bow and thus disrupt the intended line of flight of the arrow. With a finger controlled bowstring release, the arrow first flexes toward the bow then away from it. This flex is increased whenever the weight of the point is increased since the bowstring must induce motion of a greater mass. Accordingly, if a complete cycle of flex is desired by the time the arrow leaves the bow so that contact of the fletch with the bow is negligible or non-existant, a means for adjusting the flex of the arrow is needed.
Among the parameters which have in the past been varied to change the dynamic stiffness or flex without changing the length of the arrow are the point weight and the shaft stiffness. In the prior art, the archer could only change shafts or adjust the arrow by changing the point weight since most prior art replaceable nocks are of substantially identical characteristics so that a nock change made no substantial difference. If the archer wished to match the arrow stiffness with a particular bow, in the past he had no easy way to do so.
Although it is well known that arrows flex when propelled by the bowstring and continue to do so while in flight, it is not readily appreciated that the amount of flex can be controlled by adding weight to the nock. Flex in the connection between the arrow and the nock also occurs and this connection should therefore also be stiffened to compensate for the added weight. Arrow flex is ordinarily reduced by stiffening of the arrow shaft itself where the flex is known to take place. This necessarily results in significant additional arrow weight and correspondingly less arrow velocity. Consideration has been given to stiffening of the nock material with fiber reinforcement; however, this has been found to lower the overall impact resistance of the nock and eliminate desired visual transparency of the plastic which is important in determining if nock failure has taken place.
It is an objective of the present invention to provide a means of adjusting the flex or dynamic spine of the arrow to tune the arrow to the bow.
It is a further objective of the present invention to provide a means of adjusting the dynamic spine or flex without substantially changing of the location of the center of gravity of the arrow.
It is a further objective of the present invention to provide an easily replaceable arrow nock which prevents damage from incoming arrows to the shaft of an arrow shaft embedded in a target.